JP2012134927A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress vibration of a plurality of mirror members and to appropriately read an image on an original when a scanning unit including a light source irradiating the original on an original reading plate with light and the plurality of mirror members which extend in a width direction of the original and have slender plate shapes is scanned.SOLUTION: A scanning unit 10 including a light source 12 irradiating an original P on an original reading plate 11 with light and a plurality of mirror members 14 to 16 which extend in the width direction of the original and have the slender plate shapes is scanned in a direction crossing the width direction of the original. For reflecting reflected light radiated from the light source and reflected on the original by the mirror members to guide it to an imaging element section 20, recesses 14b to 16b extending in a long side direction are installed in at least centers of short sides on faces opposite to reflection faces 14a to 16a reflecting the light.

Description

  The present invention relates to an image reading apparatus used for a copying machine, a facsimile, an image scanner, and the like. In particular, a scanning unit having a light source for irradiating light on a document reading plate and a plurality of elongated plate-like mirror members extending in the document width direction is crossed with the document width direction. In the image reading apparatus in which the reflected light irradiated from the light source and reflected from the original is reflected by each of the mirror members and guided to the image sensor unit, when the scanning unit is scanned, This is characterized in that the mirror member is suppressed from vibrating so that an image on the original can be read appropriately.

  In an image reading apparatus used for a copying machine, a facsimile, an image scanner, and the like, generally, a light source for irradiating light on a document on a document reading plate and a plurality of elongated plates extending in the width direction of the document A scanning unit including a mirror member is scanned in a direction intersecting the width direction of the document, and the reflected light that is irradiated from the light source and reflected by the document is reflected by each of the mirror members and guided to the image sensor unit. In this image sensor unit, an image on a document is read.

  Here, as a drive source that scans a scanning unit including a light source and a plurality of mirror members extending in the document width direction as described above in a direction crossing the document width direction, a DC servo is used in a machine that performs high-speed scanning. Stepping motors are used in motors, popular machines and low-speed machines, and the latter stepping motors, which are particularly advantageous in terms of cost, are widely used.

  However, when the above scanning unit is scanned using such a drive source, particularly when a stepping motor is used, the vibration in the stepping motor is large, and accordingly, the mirror in the scanning unit is scanned during scanning. The vibration of the member causes blurring, etc., and the reflected light from the original cannot be appropriately reflected and guided to the image sensor unit, so that the image on the original cannot be read properly, and the read image is distorted. In addition, there is a problem that color misregistration occurs in reading a color image.

  And conventionally, as shown in Patent Document 1, by changing the thickness of the plurality of mirror members, etc., making the natural frequency in each mirror member different, and suppressing each mirror member from resonating, Proposals have been made to suppress the vibration and amplitude of each mirror member.

  However, as shown in Patent Document 1, it is troublesome and costly to vary the natural frequency of each mirror member by varying the thickness of each mirror member. It has been difficult to sufficiently suppress the vibration of the mirror member itself.

  Conventionally, as shown in Patent Document 2, a flatness reinforcing member having a flatness of 100 mR or more is tightly fixed to a surface opposite to the reflecting surface of the mirror member, and the flatness accuracy of the mirror member is not impaired. In order to improve the vibration control effect, a proposal has been made.

  However, as shown in Patent Document 2, it is troublesome and costly to fix the flatness reinforcing member as described above on the surface opposite to the reflecting surface of the mirror member. There was a problem that it was bulky as much as it was fixed closely.

JP-A-4-3366751 JP-A-8-106129

  The present invention relates to a scanning unit including a light source for irradiating light on a document on a document reading plate and a plurality of elongated plate-like mirror members extending in the width direction of the document. When scanning the above scanning unit in an image reading apparatus that scans in the direction in which the reflected light is reflected from the light source and reflected from the original is reflected by each of the mirror members and guided to the image sensor section. An object of the present invention is to suppress the vibration of the mirror member with a simple configuration so that an image on a document can be read appropriately.

  In order to solve the above-described problems, the present invention includes a light source for irradiating light on a document on a document reading plate, and a plurality of elongated mirror-like mirror members extending in the width direction of the document. The scanning unit is scanned in a direction crossing the width direction of the document, and the reflected light irradiated from the light source and reflected by the document is reflected by each of the mirror members and guided to the image sensor unit. In at least one mirror member of the plurality of mirror members, a concave portion extending in the long side direction is provided on at least the central portion of the short side of the surface opposite to the reflecting surface that reflects light.

  Here, in providing a recess extending in the long side direction on the surface opposite to the reflecting surface of the mirror member as described above, the recess extending in the long side direction at a portion other than the end on one side on the short side. However, when the scanning unit is scanned, in order to further suppress the vibration of the mirror member, the concave portion is opposite to the reflecting surface of the mirror member. It is preferable to provide it in the center part of the short side in the surface of this, and to make the thickness of the part of the both sides of the short side thicker than the thickness of this recessed part.

  Further, in order to further suppress the vibration of the mirror member when providing the concave portion extending in the long side direction on the surface opposite to the reflecting surface of the mirror member as described above, the mirror provided with the concave portion is provided. When the weight of the member is Mb, the cross-sectional secondary moment is Ib, the weight of the mirror member not provided with the recess is Ma, and the cross-sectional secondary moment is Ia, the condition of Ia / Ma ≦ Ib / Mb is satisfied. It is preferable to satisfy.

  In the image reading apparatus of the present invention, since a concave portion extending in the long side direction is provided at least in the center of the short side on the surface opposite to the reflecting surface that reflects the light in the mirror member, the cross section of the mirror member When the second moment is increased and the strength against bending is improved, the weight is reduced as compared to a flat plate-shaped mirror member not provided with a concave portion, the deflection due to its own weight is suppressed, and when the above scanning unit is scanned, The mirror member is appropriately suppressed from vibrating.

  As a result, in the image reading apparatus of the present invention, when the image on the original is read, distortion of the read image or color shift in reading the color image is suppressed, and the image on the original is read. It can be read properly.

1 is a schematic explanatory view showing an image reading apparatus according to an embodiment of the present invention. It is a schematic perspective view of the mirror member used for the image reading apparatus according to the above embodiment. The mirror member used for the image reading apparatus which concerns on said embodiment is shown, (A) is the top view which showed the surface on the opposite side to a reflective surface, (B) is a side view. In the image reading apparatus according to the above embodiment, the length of the short side of the mirror member is W, the width of the concave portion is Wx, the thickness of the mirror member in the portion where the concave portion is not provided is Tb, and the concave amount of the concave portion is Ty. The horizontal axis is X = Ty / Tb, the vertical axis is Y = Wx / W, and Y = 0.0423LnX and Y = 1.3781LnX. In the image reading apparatus according to the above-described embodiment, a cross section with respect to the weight Mb of each mirror member in which the width of the concave portion and the amount of the concave portion are changed when the concave portion extending in the long side direction is provided in the central portion on the short side. It is the graph which showed the ratio (Ia / Ma) of the cross-sectional secondary moment Ia with respect to the weight Ma to the change of ratio (Ib / Mb) of the secondary moment Ib, and the flat mirror member in which the recessed part is not provided. In the image reading apparatus according to the above embodiment, an example in which the second mirror member and the third mirror member are held by the second scanning unit is shown, and (A) is from a surface opposite to the reflecting surface of the mirror member. The schematic rear view seen, (B) is a schematic sectional view on the side surface side of the mirror member.

  Next, an image reading apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. Note that the image reading apparatus according to the present invention is not limited to those shown in the following embodiments, and can be implemented with appropriate modifications within a range not changing the gist thereof.

  In the image reading apparatus according to this embodiment, as shown in FIG. 1, a document P is placed on a document reading plate 11 made of a glass plate.

  In the image reading apparatus of this embodiment, the light source 12 that irradiates the original P with light under the original reading plate 11 and the reflection that reflects the light emitted from the light source 12 toward the original P. A scanning unit 10 including a mirror 13 and first to third mirror members 14 to 16 each having an elongated plate shape extending in the width direction of the document P is provided, and is reflected on the document P. An imaging element unit 20 is provided in which the reflected light is reflected and guided by the first to third mirror members 14 to 16 in the scanning unit 10.

  Here, in the image reading apparatus, the scanning unit 10 includes the first scanning unit 10A including the light source 12, the reflecting mirror 13, and the first mirror member 14, the second mirror member 15, and the first mirror member 15. And a second scanning unit 10B having three mirror members 16. The first scanning unit 10A and the second scanning unit 10B are separated from each other by a motor 17 such as a DC servo motor or a stepping motor. Scanning is performed in a direction crossing the direction.

  Then, in the first scanning unit 10A and the second scanning unit 10B that are scanned in this way, the light source 12 and the reflecting mirror 13 scan the light in the direction intersecting the width direction of the document P, and then the document P is scanned. The reflected light reflected from the original P is reflected by the first to third mirror members 14 to 16 and guided to the image sensor section 20. When the first scanning unit 10A and the second scanning unit 10B are scanned in the direction intersecting with the width direction of the document P in this way, the reflected light reflected from the document P is guided to the imaging element unit 20 described above. In order to keep the optical path length to a constant, the moving speed of the second scanning unit 10B is set to ½ of the moving speed of the first scanning unit 10A.

  The image sensor unit 20 includes an imaging lens 21 and an image sensor 22 that reads an image. Then, the reflected light from the original P reflected and guided by the first to third mirror members 14 to 16 as described above is imaged on the image sensor 22 by the imaging lens 21, and the original P The image in is read.

  Here, when the first scanning unit 10A and the second scanning unit 10B are scanned in the direction intersecting the width direction of the document P by the motor 17 as described above, particularly when a stepping motor is used as the motor 17, The vibration in the motor 17 is transmitted to the first to third mirror members 14 to 16 provided in the first scanning unit 10A and the second scanning unit 10B, and the first to third mirror members 14 to 16 are transmitted. When it vibrates, the reflected light from the original P is not properly reflected by the first to third mirror members 14 to 16, and the image on the original P cannot be accurately read by the imaging element unit 20.

  For this reason, in the image reading apparatus according to this embodiment, as shown in FIGS. 1 and 2, the first to third mirror members 14 to 3 are formed in an elongated plate shape extending in the width direction of the document P. 16, recesses 14 b to 16 b extending in the long side direction are provided in the central part on the short side of the surface opposite to the reflecting surfaces 14 a to 16 a.

  And when the concave portions 14b to 16b extending in the long side direction are provided in the central portion on the short side of the surfaces opposite to the reflecting surfaces 14a to 16a in the first to third mirror members 14 to 16, as described above, The cross-sectional secondary moment in each of the mirror members 14 to 16 is increased, the strength against bending is improved, and the weight is lighter than that of a flat plate having a constant thickness. As a result, when the scanning unit 10 is scanned as described above, the mirror members 14 to 16 are appropriately suppressed from vibrating, and reflected light from the document P is reflected from the first to third mirror members 14 to 14. 16, the image sensor unit 20 can accurately read the image on the original P, and the read image is distorted or the color image is read when the color image is read. The occurrence of a shift is suppressed.

Here, in each of the mirror members 14 to 16, the concave portions 14b to 16b extending in the long side direction are provided in the central portion on the short side on the surface opposite to the reflecting surfaces 14a to 16a. As shown in A) and (B), the lengths of the short sides of the mirror members 14 to 16 are W, the widths of the recesses 14b to 16b are Wx, and the mirror members 14 to 16 in the portions where the recesses 14b to 16b are not provided. Where Tb is the thickness of Tb and the amount of recesses 14b-16b is Ty, X = Ty / Tb and Y = Wx / W are
0.0423LnX ≦ Y ≦ 1.3781LnX
It is preferable to satisfy the above condition.

  If it does in this way, the deflection | deviation by the dead weight in the mirror members 14-16 in which the recessed parts 14b-16b were provided will become smaller than the flat mirror member in which the recessed part is not provided, and the scanning unit 10 is scanned as mentioned above. At this time, the vibration and amplitude in each of the mirror members 14 to 16 are reduced, and the occurrence of distortion in image reading is suppressed. In the graph of FIG. 4, the above-mentioned X = Ty / Tb is abscissa and Y = Wx / W is ordinate, and the line is represented by the expression 0.0423LnX and the expression 1.3781LnX. Line.

  In addition, for a mirror member made of a glass plate having a long side length of 300 mm, a short side length W of 20 mm, and a thickness Tb of 5 mm, a concave portion extending in the long side direction is provided at the center of the short side. In providing, the ratio (Ib / Mb) of the secondary moment of inertia Ib to the weight Mb of each mirror member was obtained by changing the width Wx of the recess and the recess amount Ty of the recess, and the results are shown in FIG. Further, the ratio of the cross-sectional secondary moment Ia to the weight Ma (Ia / Ma) was also obtained for a flat mirror member not provided with a recess, and the result is shown by a thick line in FIG.

  In FIG. 5, the ratio (Ib / Mb) of the cross-sectional secondary moment Ib to the weight Mb of the mirror member provided with the concave portion is the weight Ma of the flat plate-like mirror member provided with the concave portion indicated by the bold line. When the cross-sectional secondary moment Ia is greater than the ratio (Ia / Ma), that is, when the condition of Ia / Ma ≦ Ib / Mb is satisfied, the mirror member provided with the concave portion is bent due to its own weight. When the scanning unit 10 is scanned as described above, the vibration and amplitude of each of the mirror members 14 to 16 are reduced, resulting in distortion in image reading. To be suppressed.

  Further, when the mirror members 14 to 16 are held by the first scanning unit 10A and the second scanning unit 10B, the mounting members are brought into contact with the surfaces of the recesses 14b to 16b of the mirror members 14 to 16, respectively. In this manner, the mirror members 14 to 16 can be held by the first scanning unit 10A and the second scanning unit 10B by this mounting member.

  For example, when the second scanning member 10B is held by the second mirror member 15 and the third mirror member 16, in the example shown in FIGS. 6A and 6B, the second and third mirror members 15 are used. A pair of holding plates 18 are provided in the long side direction of the second and third mirror members 15 and 16 so as to hold the ends on both sides of the long side direction of the second and third mirror members 15 and 16, and the second and second At the end portions on both sides in the long side direction of the third mirror members 15 and 16, the mounting members 19 are brought into contact with the respective surfaces at both end portions of the concave portions 15b and 16b of the second and third mirror members 15 and 16. The mounting plate 18 is mounted in a mounting hole 18a provided in the holding plate 18. The mounting member 19 and the holding plate 18 sandwich the both ends of the second and third mirror members 15 and 16 in the long side direction. 2 mirror member 15 and third mirror member 15 And over member 16 so that is retained in the second scan unit 10B. If it does in this way, both the long-side direction both ends of the 2nd, 3rd mirror members 15 and 16 will be appropriately hold | maintained by said mounting member 19 and the holding | maintenance plate 18, and it will become 2nd as mentioned above. When the scanning unit 10B is scanned, the second and third mirror members 15 and 16 are appropriately suppressed from vibrating, and the mounting member 19 does not cause the second scanning unit 10B to be bulky.

  In this example, the mounting member 19 is simply attached to both end portions of the recesses 15b, 16b of the second and third mirror members 15, 16, but the second, third mirror members 15, It is also possible to mount the attachment member 19 between the pair of holding plates 18 so as to fit into the entire 16 recesses 15 b and 16 b.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Scanning unit 10A 1st scanning unit 10B 2nd scanning unit 11 Document reading plate 12 Light source 13 Reflecting mirror 14-16 First to third mirror members 14a-16a Reflecting surface 14b-16b Recessed part 17 Motor 18 Holding Plate 18a Mounting hole 19 Mounting member 20 Imaging element section 21 Imaging lens 22 Imaging element P Document Tb Thickness of the portion where the concave portion of the mirror member is not provided Ty Depression amount of the concave portion of the mirror member W Length of the short side of the mirror member Wx Mirror member recess width

Claims (3)

  A scanning unit including a light source for irradiating light on the original on the original reading plate and a plurality of elongated plate-like mirror members extending in the width direction of the original is scanned in a direction crossing the width direction of the original. In the image reading apparatus in which reflected light that is irradiated from the light source and reflected by the document is reflected by each of the mirror members and guided to the image sensor unit, light is emitted from at least one of the plurality of mirror members. An image reading apparatus characterized in that a concave portion extending in the long side direction is provided at least in the center of the short side of the surface opposite to the reflecting surface that reflects the light.   2. The image reading apparatus according to claim 1, wherein the concave portion is provided in a central portion on the short side of the surface opposite to the reflecting surface of the mirror member, and the thickness of both side portions on the short side is the concave portion. An image reading apparatus having a thickness greater than that of the image reading apparatus. 3. The image reading apparatus according to claim 1, wherein the weight of the mirror member provided with the recess is Mb, the second moment of the section is Ib, the weight of the mirror member without the recess is Ma, and the section thereof. When the second moment is Ia,
Ia / Ma ≦ Ib / Mb
An image reading apparatus satisfying the following condition.

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